PT QUIZ

بهمن ۱۴۰۳

در شرایطی که اقتصاد کشور با چالش‌های متعدد دست‌وپنجه نرم می‌کند، دو مسئله‌ی مهم "عدم کفایت دستمزدها" و "کمبود نیروی کار" ( نظرخودم :  اشتباه بزرگ در اخراج افاغنه ) به‌طور فزاینده‌ای در حال گسترش است. این وضعیت نه‌تنها معیشت خانوارها را تحت تأثیر قرار داده، بلکه در بخش‌های مختلف تولید و خدمات نیز بحران ایجاد کرده است.

آمارهای میدانی به راحتی نشان می دهد که بسیاری از کارگران و کارمندان بر این باورند که دستمزدهای فعلی توان تأمین هزینه‌های زندگی را ندارد ( نظر خودم :  پس علت تولد نوزادهای جدید در این تورم چیست ؟  احتمالاً بخاطر دفاع از کشور در آینده ). تورم روزافزون و افزایش قیمت کالاهای اساسی باعث شده که حتی اقلام ضروری از دسترس بخش قابل‌توجهی از جامعه خارج شود. کارگران می گویند با این حقوق‌ها نمی‌توان زندگی کرد. هزینه اجاره خانه، آموزش فرزندان و خوراک هر روز بیشتر می‌شود، اما حقوق ما ثابت مانده است.

Liquid penetrant inspection is a nondestructive testing method used to detect surface defects in materials. In this process, a liquid penetrant is applied to the surface of the material and allowed to seep رسوخ کند into any surface defects. To ensure effective penetration, the liquid must have a low surface tension. Low surface tension allows the liquid to spread evenly over the surface and penetrate into small cracks and defects. Therefore, a low surface tension is an important requirement for the liquid used in liquid penetrant inspection.

Advantages of the Penetrant Process

The following are advantages of the liquid penetrant process:

1. very small surface discontinuities can be detected,

2. a wide variety  of materials can be tested,

3. complex geometrical shapes can be inspected in a single operation,

4. various sensitivities and processing methods are available,

5. it is relatively easy to use,

6. it can be portable

7. when compared to other testing methods, it has a low cost.

Disadvantages of the Penetrant Process

The following are disadvantages of the liquid penetrant process:

1. porous materials cannot be tested

2. surfaces must be clean and free of paint, coatings, soil, moisture and contaminants

3. it cannot be used following metal smearing operations such as shot peening, sand blasting, certain machining operations (unless material is acid etched to remove smeared metal)

4. some materials (rubber and plastics) may be adversely affected by the penetrant's petroleum base;

5. it is very dependent on operator skill

6. some penetrant products use ingredients that may cause skin irritation under prolonged contact if proper protective clothing is not worn.

If a system is too sensitive, the results may be misleading ( گمراه کننده ) and time will be wasted ( تلف شود ) in the evaluation process. If the system is not sensitive enough, rejectable defects could remain undetected.

The sensitivity of a liquid penetrant system refers to its capability to detect small defects. This means that a highly sensitive system can identify even the smallest flaws عیوب  or imperfections in the material being tested. Contrast ratios and color intensity may contribute to the system's effectiveness, but the primary factor determining sensitivity is its ability to detect small defects. The frequency of black-light used is not mentioned in the question and therefore cannot be considered as a factor in determining sensitivity.

The tendency تمایل of a liquid penetrant to enter a discontinuity is primarily related to the capillary forces. where a liquid can be drawn into narrow spaces or tubes against the force of gravity. In the case of liquid penetrant testing, capillary forces allow the penetrant to flow into small cracks or defects in a material, making them visible during the inspection process. 

Liquid penetrant testing is a nondestructive testing method used to detect surface discontinuities in materials.  allowing it to seep into any surface cracks or defects, and then removing the excess penetrant. The penetrant is typically brightly colored to make it visible under UV light. However, liquid penetrant testing is not capable of accurately measuring the depth of a crack or discontinuity. It can only detect the presence of surface defects, making it more suitable for finding shallow surface discontinuities rather than measuring the depth of cracks.

it is important to avoid using penetrants containing sulphur and chlorine on nickel surfaces to maintain their integrity and prevent any potential harm.

A water tolerance test is used to determine how much water a postemulsifiable penetrant or a hydrophilic emulsifier can tolerate before becoming unusable. This test helps to establish the maximum amount of water that can be present in the penetrant or emulsi¦er without affecting its effectiveness. By conducting this test, one can ensure that the penetrant or emulsifier is able to withstand مقاومت a certain level of water contamination آلودگی آب and still perform its intended function عملکرد موردنظر.

Contact angle is determined by the balance between the adhesive forces between the liquid and the surface, and the cohesive forces within the liquid. A high contact angle indicates that the liquid is less likely to spread out on the surface, while a low contact angle indicates that the liquid will spread out more easily. The contact angle is important in various applications, such as determining the wettability of a surface or understanding the behavior of liquids on different materials

The ability of the penetrant to enter the discontinuity is based on surface tension; however, the speed at which it enters is determined by viscosity.

A hydrometer is used to measure the specific gravity of a liquid. It works based on the principle that the density of a liquid is directly proportional to its specific gravity. The hydrometer is a cylindrical glass tube with a weighted bulb at the bottom. When placed in a liquid, it floats and the level at which it sinks indicates the specific gravity of the liquid. Therefore, a hydrometer is the correct tool for checking specific gravity.

Immersion dwell is a technique used in non-destructive testing where the test part is immersed in a liquid medium for a prolonged period. This method is employed when there is a need for extended dwell times to ensure thorough inspection. The other options mentioned, such as shallow and wide discontinuities and large numbers of test parts, do not specifically require the use of immersion dwell.

dilation of the pupils enables the operator to see better in the darkened environment and detect any visible dye penetrant indications. Therefore, a minimum of three minutes is required to allow the operator's eyes to fully dilate and achieve maximum seeing in the darkened inspection area.

Type of Penetrant

Penetrant can be fluorescent, visible or dual mode dye that has both visible and fluorescent properties

Fluorescent penetrant contains a dye that is visible under UV-A light. To view the indications, inspection is performed in a darkened area with an ultraviolet light source

Fluorescent penetrants have the advantage of being able to detect smaller indications more easily compared to visible dye penetrants. This is because fluorescent penetrants emit a bright glow under UV light, making even small indications more visible and easier to identify during inspection.

A black light filter is not necessary to activate the fluorescent penetrant dye because the dye is activated by the UV light emitted by the black light bulb itself. It is also not necessary to provide a contrasting background on the material surface as the black light already highlights any fluorescence present on the surface. Additionally, it is not needed to protect the black light bulb from scratches and breakage as this is not its purpose.

The black-light intensity is stated as a minimum of 1000 microwatts per centimeter squared in order to ensure that the fluorescent dye reaches its peak fluorescence. When the black-light intensity is at this level, it provides the optimal conditions for the dye to emit the brightest fluorescence, making it easier for the operator to detect any defects or irregularities on the material surface. This level of intensity ensures that the dye is fully activated and visible, allowing for accurate inspection and evaluation.

Visible penetrant uses a red, orange or purple dye that is highly visible when contrasted against a white developer coating the part surface. Inspection must be performed under white light.

Type I : Advantages of Fluorescent Liquid Penetrants

fluorescent liquid penetrant testing is more sensitive to small discontinuities than visible dye.

Advantages of Visible Dye Penetrants

It does not require a darkened area or a source of electric power for illumination ( روشنایی ). For this reason, it is more often used as a portable testing tool in the shop or field

Disadvantages of penetrant Type : 

-Type I , Fluorescent : 

--Requires special lighting

--Requires electricity

-Type II , Visible Dye

--Less sensitive than Type I

--Does not perform well for wide, shallow discontinuities

Penetrant class is not divided into performance grades as is fluorescent liquid penetrants.The visibility of the indications with respect to the white developer background is a key factor in successfully revealing tight discontinuities. 

زمان ماندگاری ماده نافذ روی قطعه مورد آزمون

Penetrant Dwell

The total time the penetrant remains on the part surface is the penetrant dwell. The time required for a penetrant to enter a discontinuity is dependent on temperature, the type of discontinuity and the possibility of contaminants entrapped within discontinuities. Large, shallow discontinuities require less dwell time than small, tight cracks. Discontinuities free from contaminants require less dwell time than discontinuities with entrapped soil because it is easier for the penetrant to enter them.

The standard minimum dwell is 5 min unless testing in service parts. If service fatigue cracks are suspected, the minimum dwell time required is often 2 h, but for stress corrosion up to 4 h may be required. When the dwell exceeds 1 h, applying fresh penetrant every hour improves the rate of penetration.

Temperature

The temperature of the penetrant materials and the part must be within an acceptable range for processing. ASTM E 1417 specifies a temperature range of 4 to 52 °C (40 to 125 °F).

The viscosity of most liquids, including penetrants, increases at low temperatures. If a part is quite cold, under 16 °C (60 °F) for example, the liquid penetrant may become chilled and thickened when applied, making the dwell time for very fine discontinuities longer than for parts at higher temperatures. If a part or liquid penetrant is too hot, the volatile components of the liquid penetrant may evaporate, changing the ability for revealing small discontinuities. Material temperatures from 10 to 52 °C (50 to 125 °F) produce optimum results with conventional liquid penetrants,

Most industry and military specifications limit acceptable water temperature to 10 to 38 °C (50 to 100 °F) at a pressure not to exceed 276 kPa (40 psi). The spray nozzle should be a minimum of 30 cm (12 in.) from the part at an angle between 45 and 70 degrees.

روش حذف ماده نافذ اضافی

Penetrant Removal Method

Excess penetrant is removed by water wash, hydrophilic emulsification, lipophilic emulsification, or solvent wipe.

The penetrant must be removed from the part surface without removing it from within a discontinuity. An optimum amount of removal must be obtained. Too little removal will cause an excessive penetrant background and indications will be indistinguishable from the part surface. If too much is removed from the discontinuity, a weak indication or no indication will be formed. The methods for removing surface penetrant and the SAE AMS 2644 designation are:

1. Method A - Water Washable

2. Method B - Lipophilic Emulsifier

3. Method C - Solvent Removable

4. Method D - Hydrophilic Emulsifier

Fluorescent penetrant should be removed in a darkened area equipped with ultraviolet lighting regardless of the removal method.

Water Washable (Method A)

Water washable penetrants contain emulsifying agents that make the oil miscible (mixable) with water. The penetrant may be removed with a manual or automatic coarse water spray, by immersion in an air agitated water wash or by manually wiping.

The rinsing operation must be monitored closely to avoid overwashing. Washing should be stopped as soon as an acceptable background level is observed.

Lipophilic Emulsifier (Method B) چربی دوست

Removal is performed by introducing an oilbased emulsifier as a separate process step. Lipophilic emulsifier diffuses in to the surface penetrant. It is usually applied by immersion; brushing or wiping may cause streaking due to uneven emulsification and are not recommended. This system offers more control and has fewer problems with over and under washing compared to the water washable method. The emulsifier dwell may be anywhere between 5 s up to 5 min.

ASTM E 1417 limits lipophilic emulsifiers to a 3 min maximum dwell time. Finding the optimum time for specific conditions is generally accomplished through experimentation. Experience under similar circumstances related to the type and size of suspected defects, surface roughness of the part, temperature of materials, water contamination levels of the penetrant and emulsifier can be used for a guideline. If the emulsification time is either too short or too long, the part must be entirely cleaned and reprocessed with an adjusted emulsifier dwell.

Following the appropriate dwell, the part should be quickly sprayed with water wash to stop the diffusion process. Once the diffusion process is halted, the emulsified penetrant is rinsed using the same methods as the water washable method.

The postemulsification test is used to detect defects or cracks in materials by applying a penetrant, emulsifying it, and then removing the excess. If the emulsifying time is too long, it can cause the penetrant to be completely removed from the cracks or defects, rendering the test ineffective as it will not be able to detect any flaws عیوب

تست را بی اثر می کند زیرا قادر به تشخیص هیچ نقصی نخواهد بود

Having an ultraviolet light installed at the wash station allows for the inspection of parts without the need for drying. This is because ultraviolet light can reveal any fluorescent dye penetrant that may be present on the parts. By using the ultraviolet light, one can determine if the wash cycle has been effective in removing any remaining dye penetrant from the parts. This helps ensure that the parts have been properly cleaned and prepared for further processes or use.

emulsifier time is extremely important and will greatly affect test results. This implies that the amount of time the emulsifier is allowed to act on the surface has a significant impact on the outcome of the test. The longer the emulsfier time, the better the results are expected to be.

Solvent Removable (Method C)

Solvent remover is usually supplied in aerosol spray cans. The solvent works by diluting the surface penetrant. The part is first wiped with clean, dry, lintfree cloths or towels. After the major portion of penetrant has been wiped from the surface, the surface should be wiped with a clean cloth, lightly sprayed with solvent, until just a trace of penetrant is observed on the cloth. Extreme caution must be used to avoid excessive removal.

Using an excessive amount of solvent when using a solvent-removable penetrant can have negative effects. It can lead to excessive removal of the penetrant from the surface, making it difficult to detect any defects. This can result in false-negative results and compromise the effectiveness of the inspection process. Therefore, it is generally accepted that using an excessive amount of solvent should be avoided as a precautionary measure.

Water-soluble and water-suspensible developers also require the correct drying of the test parts after applying the developer to prevent streaking ( رگه شدن ) and running ( جاری شدن)  of the developer coating. 

Note: Flowchart shows parts being dried before dry powder and nonaqueous developer, but dried after water-soluble and water suspendable developer.

Developers : 

Dry developer is the most suitable developer for parts that are complex or have rough surfaces ,  Aqueous developer is a water-based developer that is more suitable for smooth surfaces, while non-aqueous developer is a developer that is not water-based and may not adhere as well to complex or rough surfaces.

Non-aqueous developers are typically solvent-based and have a higher sensitivity compared to dry and aqueous developers. They are able to detect smaller defects and provide higher contrast images. Dry developers are typically used for magnetic particle testing and do not provide as high sensitivity as non-aqueous developers. Aqueous developers are water-based and have lower sensitivity compared to non- aqueous developers. Therefore, the non-aqueous developer is the most sensitive option.

Non-aqueous->aqueous->dry

1-Difficulties with removal of a postemulsifiable penetrant during the rinse operation can be overcome by:

a. reapplying a coating of emulsifier.

b. using conditioned (soft) water during the washing operation.

c. cleaning, then completely reprocessing the part using a longer emulsification time.

d. increasing the water temperature during the washing operation.

2-Which of the following is an advantage of a fluorescent water washable penetrant system compared to a fluorescent postemulsifiable penetrant system?

a. Water washable is superior for testing critical in service parts.

b. Water washable has fewer processing steps.

c. Only wet developer may be used with postemulsifiable penetrants.

d. Water washable penetrants will more readily detect fine, tight cracks in weldments.

3-When using the visible, solvent removable process, after the penetrant dwell time, excess penetrant is removed by:

a. spraying solvent on the part and then wiping with a clean, dry rag or paper towel.

b. wiping off excess penetrant with a clean, dry rag or paper towel, moistening the part with solvent and rewiping the part.

c. wiping off excess penetrant with a clean, dry rag or paper towel, moistening a clean cloth with solvent and rewiping the part.

d. wiping off excess penetrant with a clean, dry rag or paper towel, then rewiping with a cloth soaked with solvent.

4-Which of the following is not an advantage of postemulsifiable fluorescent penetrants?

a. High sensitivity level to detect very fine defects.

b. They are easily removed with water after proper emulsification dwell time.

c. They are easily removed from sand castings after proper emulsification dwell time.

d. They have higher tolerance to variations in the removal process when compared to water washable penetrants

5-One method for applying dry developer to a localized area of a large part is with:

a. a brush.

b. a powder bulb.

c. an aerosol can.

d. an immersion tank.

6-Prewash and postwash stations are anadvantage when using which of the following penetrant methods?

a. Visible, lipophilic postemulsifiable.

b. Fluorescent, hydrophilic postemulsifiable.

c. Visible, water washable.

d. Fluorescen , lipophilic postemulsifiable.

7-The specific gravity of wet developer is measured with a:

a. developer gage.

b. hydrogage.

c. balance scale.

d. hydrometer.

8-Which of the following describes the comparator that is used to monitor the process performance of the penetrant system?

a. A panel with one half chrome plated containing five crack centers and the other half grit blasted.

b. A cracked aluminu m block with a groove in the center.

c. A chrome plated panel with fine cracks across the face to a depth equal to the plating thickness.

d. Ceramic coated block with fine cracks extending around the entire panel.

9-Ultraviolet light intensity is measured with:

a. a digital or analog UV-A meter.

b. a photographic light meter.

c. an infrared meter.

d. a standard white light meter.

10-What instrument is used to check hydrophilic emulsifier concentration?

a. A hydrometer.

b. A capillary fill barometer.

c. A centrifuge tube.

d. A refractometer.

11-An important difference between non water- washabIe penetrants and water-washabIe penetrants is that:

a. water-washabIe penetrants contain an emuIsifier whiIe non water- washabIe penetrants do not

b. the viscosity of the two penetrants is different

c. the coIor of the two penetrantsis different

d. non water-washabIe penetrants are more easiIy removed than water- washabIe penetrants

12-Which of the foIIowing characteristics ( ویژگی های زیر ) are normaIIy considered when seIecting the type of penetrant to be used a penetrant test?

a. removaI characteristics of the penetrant

b. the fIash point of the penetrant

c. the cost of the penetrant

d. aII of the above

13-Which materiaIs shouId be avoided in the penetrant system when testing titanium aIIoys?

a. carbon or oiI

b. haIogenated soIvents 

c. emuIsifier or oiI

d. fIuorescent agents

14-Which of the foIIowing is an advantage of visibIe dye penetrants over fIuorescent penetrants?

a. smaII indications are more easiIy seen

b.they can be used on anodized and chromate surfaces

c. they make Iess background on rough surfaces

d. no speciaI Iighting is required

15-Which of the foIIowing is an advantage of soIvent-wipe methods over water washing?

a. no speciaI Iighting is necessary during inspection

b. they provide a quicker penetration of smaII openings

c. smaII indications are more easiIy seen

d. they can easiIy be carried out in the fieId and to remote areas

16-The tendency (  تمایل ) of a Iiquid penetrant to enter a discontinuity is primariIy reIated to the:

a. viscosity of the penetrant

b. capiIIary forces

c. chemicaI inertness of the penetrant

d. specific gravity of the penetrant

17-The emuIsifier is used :

a. to wash the penetrant out of discontinuities

b. to aid in washing off the surface of parts when using either the water or soIubIe penetrants

c . to emuIsify the oiI-soIubIe penetrant, thereby making it water-washabIe

d. to pre-cIean parts before appIying penetrant

18-Why is it advisabIe to have a bIack Iight instaIIed at the wash soIution?

a. so inspection can be done without drying parts

b. to speed the bIeeding penetrant out of defects

c. to check the effectiveness of the wash cycIe

d. to determine if parts have been covered with penetrant

19-The prime purpose of the bIack Iight for fIuorescent penetrant inspection is to :

a. magnify indications

b. make the indication visibIe

c. develop indication

d. speed up inspections

20-AII of the foIIowing methods are recommended to remove grease from the surface of a penetratnt test specimen except:

a. vapor degreasing

b. aIkaIine cIeaning

c. cIeaning with soIvent-type materiaI

d. hot water rinsing

21-The penetrant indication for a coId shut on the surface of a casting wiII be a:

a. dotted or smooth continuous Iine

b. cIuster of smaII indications

c. rough deep indication

d. Iarge buIbous indication

22-When improper processing causes inspection difficuIties, what shouId the inspector do?

a. swap parts with a soIvent

b. use a correct bIeed-back procedure

c. erase non-reIevant fIuorescence

d. reprocess the part

23-Which of the foIIowing is most IikeIy to render the post-emuIsification test in effective?

a. the penetrant time is too Iong

b. the deveIoping time is too Iong

c. the emuIsifying time is too Iong

d. none of the above

24- Which of the statements below applies to the liquid penetrant method of testing ?

a. the penetrant test method is less flexible that the eddy current test method

b. the penetrant test method is less reliable that the magnetic particle method for finding surface defects in ferromagnetic materials

c. the penetrant test method will not detect fatigue cracks

d. the penetrant test method is more reliable that radiographic testing when attempting to defect minute surface discontinuities

25-Developer assists in the detection of the visible dye penetrant test indications by:

a. providing a clean surface

c. providing a dry surface 

d. emulsifying the penetrant bleed-out

b. providing a contrasting background

26-The purpose for using a developer on a test specimen is to: 

a. promote penetration of the penetrant

b. absorb emulsifier residues

c. absorb penetrant from discontinuities and to provide a contrasting background

d. help to dry the surface for better observation

27-Which of the following reasons best describes why excessive drying of a part should be avoided? 

a. the extra time required is wasted

b. the developer may lose its blotting ability

c. a reduction in resolution may result

d. the excess developer may be difficult to remove

28-Which of the following practices should be avoided when performing a penetrant test?

a. applying emulsifier by dipping the part in emulsifier

b. applying developer by spraying the part with developer

c. removel of water-washable penetrant with a water spray

d. applying emulsifier with a brush

Cause : Brushing the emulsifier on to the part is not recommended either because the bristles of the brush may force emulsifier into discontinuities, causing the entrapped penetrant to be removed.

29-Which of the following penetrant systems is generally considered to be the least ( کمترین ) sensitive?

a. water-washable , visible dye

b. solvent removable , visible dye

c.water-washable , fluorescent dye

d. post-emulsification , visible dye

30-A red against white background discontinuity image is most likely to be seen when:

c. fluorescent post-emulsification penetrants are used

a. dry developers are used

d. wet developers are used

b. visible dye penetrants are used

31-When using wet developer:

a. a thick layer of developer is better than a thin layer for showing very fine cracks

b. compressed air should be used to remove excess developer

c. a black developer will show better contrast than a white developer

d. a thin layer of developer is better than a thick layer for showing very fine ( ریز  )cracks

32-A serious loss of water in a wet developer mix or an excessive over-concentration of developer powder can cause:

a. a loss of fluorescenceduring the inspection operation

b. nonrelevant indications

c. cracking of the developer coating during the drying operation

d. none of the above

33-Which of the following statements does not apply to developers used during penetrant testing?
a. Developers are normally highly fluorescent
b. Some developers furnish a contrasting background during inspection
c. Developers absorb or blot the penetrant that remains in discontinuities after the excess penetrant has been removed
d. Non aqueous developers are better suited for detecting fine crack

34-In penetrant testing, the time period from developer application to inspection is often referred to as the:

a. emulsification

b. development time

c. dwell time 

d. none of the above

35-In penetrant testing, developers should be able to perform all of the following functions except:

a. blotting penetrant from discontinuities

b. aiding in providing an image of a discontinuity

c. adding fluorescence to penetrants

d. helping control bleedout

36-Penetrants may be classified or subdiyided by the method used to remove excess penetrant. Which of the following is a proper classification in accordance with this statement?

a. nonsolvent removable

b. vapor degreased

c. water-washable

d. brush remoyable

37-When drying parts during a penetrant test, the parts:

a. are normally dried at room temperature

b. are normally dried by a circulating hot-air dryer

c. should be dried in an oven set at a temperature of 54 oC (130 °F)

d. should be dried by cool forced air

38-When using dry developer, the drying operation isperformed:

a. immediately after removal of excess penetrant

b. before the inspection step

c. thoroughly

d. all of the above

39-A good penetrant must do all of the following exeept:

a. be able to readily penetrate very fine openings

b. evaporate very rapidly

c. be able to remain in relatively coarse openings

d. be easily removed from the surface after testing

40-Which of the following is a disadvantage of using the Iiquid penetrant testing method?

a. the liquid penetrant test method is adaptable to produetion inspeetion of small parts

b. liquid penetrant testing can locate fine cracks

c. the liquid penetrant test method is a relatively simple test method

d. the Iiquid penetrant test method is not effective at all temperatures

41-Cleaning of the part prior to penetrant inspection is:

a. not required

b. important because if the part is 110 t clean, the developer cannot be improperlyapplied

c. essential because surface contaminants may prevent penetrant from gaining access to discontinuities

d. required to eliminate possibility of showing nonrelevant indications

42-When using fluorescent water-washable penetrant, adequate rinsing of the part is assured by:

a. timing of finse cycle

b. scrubbing of part surface

c. rinsing under ultraviolet light

d. using high pressure air with water

43-Black light is considered to be in the range of:

a. Long wavelength ultraviolet

b. Short wavelength ultraviolet

c. Short wavelength infrared

d. 500 to 800

44-Black light used in penetrant testing has its peak at:

a. 5550 angstroms (555 nm)

b. 4850 angstroms (485 nm)

c. 4250 angstroms (425 nm)

d. 3650 angstroms (365 nm)

45-Both fluorescent and visible dye penetrants are identified by:

A. Dwell times

B. Viscosity

C. Method of application

D. Method of Removal

The method of removal can vary depending on the type of penetrant used and the specific application. It is an important factor to consider as it can affect the overall effectiveness and efficiency of the inspection process

46-Acids and chromates should not be left on the surface of parts that will be inspected with a water-washable fluorescent penetrant because:

a. They may prevent the penetrant from entering any discontinuities

b. They may reduce the bleed-out

c. They may kill the fluorescence of the penetrant 

d. They may produce non-relevant

47-The ability of a liquid to wet a surface is measured by contact angle, i.e. the angle between the liquid and the surface at the point of contact as the liquid advances. Good penetrants should have:

a. A very small contact angle

b. A very large contact angle

c. A contact angle of approximately 45 degrees

d. A contact angle greater than 90

A large contact angle would indicate poor wetting ability and limited penetration. 

48-Which of the following characteristics ویژگیهای does not apply to liquid penetrant testing?

A. This method can accurately measure the depth of a crack or discontinuity

B. This method can be used for on-site testing of large parts

C. This method can be used to ¦nd shallow surface discontinuities

D. This method can be made more or less sensitive using different penetrant

49-Which of the following is an advantage of fluorescent penetrants over visible dye penetrants?

A. The inspection can be carried out in a well-lit area

B. Smaller indications are more easily seen

C. They can be used where contact with water is objectionable

D. They are less sensitive to contamination of dicontinuities

50-Sulphur and chlorine found in penetrants are detrimental to:

A. Aluminum

B. Iron

C. Nickel

D. Both (a) and

51-Emulsifier time:

a. Is important but not critical 

b. Is the time needed to rinse the emulsi¦er and excess penetrant from the surface

c. Is extremely important and will greatly affect test

d. Should be as long as possible

52-When penetrant testing, the temperature of the test area should not be lower than:

A. 30 degrees Celsius

B. 65 degrees Celsius

C. 10 degrees Celsius

D. 5 degrees Celsius

If the temperature is too low, the penetrant may not flow properly and the defects may not be detected.

53-Which of the following is generally accepted as the most important precaution when using a solvent-removable penetrant?

a. Do not apply an excessive amount of emulsifier

b. Do not use insufficient rinse pressure

c. Do not use excessive amount of solvent

d. Both (b) and (c)

54-Contact angle relates to:

a. The temperature at which a liquid will ignite and burn when exposed to an open §ame

b. The angle of the water spray nozzle for removing liquid penetrant

c. The angle at which a liquid sits on a material surface

d. None of the above

55-sensitivity of a liquid penetrant system is determined by:

A. Contrast ratios

B. Colour intensity

C. Ability to detect small defects

D. Frequency of black-light used

56-Which of the following developers is most suitable for parts that are complex or have rough surfaces?

A. Dry developer

B. Aqueous developer

C. Non-aqueous developer

D. None of the above

57-Wich of the following developers is the most sensitive?

A. Dry developer

B. Aqueous developer

C. Non-aqueous developer

D. None of the above

58-The most important property that enables the penetrant to enter into a discontinuity is:

A. Flash point

B. Penetrability

C. Viscosity

D. Surface tension

59-Dark adaptation is stated by most codes as a minimum of three minutes. Why?

a. To allow the operator's eyes time to contract for maximum seeing in the darkened inspection area

b. To allow the operator's eyes time to dilate for maximum seeing in the darkened inspection area

c. To allow the operator's eyes time to expand for maximum seeing of visible dye penetrant indications

d. To allow the operator's eyes time to contract for maximum seeing of §uorescent dye penetrant indications

60-Black-light intensity is stated as a minimum of 1000 microwatts per centimeter squared. Why?

A. To provide adequate visible light in the darkened viewing booth

B. The assist the operator when removing excess §uorescent penetrant from the material surface

C. To cause the §uorescent dye in the penetrant to "glow"

D. To ensure the fluorescent dye reaches its peak fluorescence 

61-The function of an emulsifier is to:

a. Help the penetrant enter a discontinuity by reducing the penetrant's surface tension

b. Mix directly with a fluorescent penetrant to increase its fluorescence 

c. Render the excess post-emulsifiable penetrant water- washable

d. Blot the penetrant back to the surface to produce an indication

62-Pre-cleaning in PT refers to:

a. Ensuring that the surface of the material is free of contaminants

b. Ensuring the penetrants are free of contaminants

c. Ensuring that a discontinuity is free of contaminants آلودگی

d. Both (a) and (c)

63-Dwell time is : 

a. The length of time the emulsifier is left on a material surface

B. The length of time a developer is left on a material surface

c. The length of time a penetrant is left on a material, to enter into a near-to-surface discontinuity

d. None of the above

64-The physics that enables the penetrant to enter into a discontinuity is called:

A. Caterpillar force

B. Gravitational force

C. Capillary force

D. None of the above

-The most important factor which determines the speed penetrant enters a discontinuity is based on viscosity.

A. True

B. False

-The amount of white light in a darkened inspection area must not exceed 2 ftc

A. True

B. False

-Developing time is a minimum of one-half of the penetrant dwell time.

A. True

B. False