1103 A New Experimental Approach for Measuring Friction Coefficients of Threaded Fasteners Focusing on the Repetition of Tightening Operation and Surface Roughness

2014 ◽  
Vol 2014.89 (0) ◽  
pp. _11-3_
Author(s):  
Hiromu KAWABAYASHI ◽  
Masataka NOMURA ◽  
Toshimichi FUKUOKA
Keyword(s):  
Surface Roughness ◽  
Experimental Approach ◽  
Friction Coefficients ◽  
Threaded Fasteners

A New Experimental Approach for Measuring Friction Coefficients of Threaded Fasteners Focusing on the Repetition of Tightening Operation and Surface Roughness

2013 ◽  
Author(s):  
Toshimichi Fukuoka ◽  
Masataka Nomura ◽  
Hiromu Kawabayashi
Keyword(s):  
Surface Roughness ◽  
Experimental Approach ◽  
High Accuracy ◽  
Strain Gages ◽  
Simple Test ◽  
Friction Coefficients ◽  
Threaded Fasteners ◽  
Loaded Surface ◽  
Experimental Errors ◽  
Easy Operation

Torque method is widely used when tightening threaded fasteners. Although it has a great advantage of easy operation, the scatter of bolt preloads inevitably occurs due to the scatter of friction coefficients. Friction coefficients on the contact surfaces are affected by various factors such as joint materials, surface roughness, tightening speed, etc. To evaluate the effects of those factors with high accuracy, experimental errors must be suppressed as low as possible. In this study, a new simple test equipment for measuring the friction coefficients is designed, in which the strain gages are attached to the equipment to eliminate the experimental errors caused by the gages being attached to each test specimen. Using the equipment, friction coefficients on the thread surface and nut loaded surface are measured separately. Experimental results show that the surface roughness has a smaller effect when using threaded fasteners made of stainless steel than the case of carbon steel fasteners. As for the repetition of tightening operations, it is found that the removal of metal power, which is generated by the galling between the mating surfaces, is effective for reducing the scatter of friction coefficients.

Surface damage characterization of photodegraded low-density polyethylene by means of friction measurements

2019 ◽  
Vol 39 (9) ◽  
pp. 805-812
Author(s):  
Toshio Igarashi ◽  
Soichiro Ohno ◽  
Sayaka Oda ◽  
Satoru Hirosawa ◽  
Yusuke Hiejima ◽  
...  
Keyword(s):  
Surface Roughness ◽  
Irradiation Time ◽  
Polymeric Materials ◽  
Optical Measurements ◽  
Low Density Polyethylene ◽  
Mean Deviation ◽  
Low Density ◽  
Friction Coefficients ◽  
Brittle Transition ◽  
Friction Measurements

Abstract Friction measurements have been carried out to characterize surface damages during photodegradation of low-density polyethylene. The average and mean deviation of the friction coefficients increase with the irradiation time in the early stage of photodegradation processes, indicating the increase in the surface roughness, whereas the mechanical properties remain essentially unchanged. In the following stage, where the ductile-brittle transition takes place, the mean deviation of the friction coefficients shows an appreciable decrease with maintaining almost constant average values, suggesting that the surface becomes more homogeneous. Beyond the ductile-brittle transition, both of the average and mean deviation of the friction coefficients gradually increase with the irradiation time, indicating further enhancement of surface roughness, followed by formation of surface cracks. The soundness of the friction measurements is confirmed by comparing with optical measurements of the surface roughness, and it is suggested that the present method gives a convenient and sensitive method of detection for degradation in polymeric materials.

Experimental Evaluation of Surface Roughness in Orthogonal Micro-Milling Processes

2012 ◽  
Vol 217-219 ◽  
pp. 1912-1916
Author(s):  
Ji Hua Wu
Keyword(s):  
Surface Roughness ◽  
Feed Rate ◽  
Experimental Approach ◽  
Critical Role ◽  
Cutting Speed ◽  
Chip Thickness ◽  
Micro Milling ◽  
Surface Model ◽  
Material Grain Size

Surface roughness plays a critical role in evaluating and measuring the surface quality of a machined product. Two workpiece materials have been investigated by experimental approach in order to gain a better understanding of their influence on the obtained surface roughness in the micro-milling processes. The experimental results show that: surface topography is completely different for different materials at the same cutting speed and feed rate; surface roughness increases with an increase of material grain size. Surface roughness decreases to a lowest value, and then increases with an increase of the feed rate. A new surface model to illustrate the influence of material and uncut chip thickness was developed. The model has been experimentally validated and shows more promising results than Weule’s model.

Robustness of polyisobutylene for friction coefficients between bearing surfaces of bolted joints

2019 ◽  
Vol 234 (1) ◽  
pp. 50-62
Author(s):  
Shinji Hashimura ◽  
Toshiumi Miki ◽  
Takefumi Otsu ◽  
Kyoichi Komatsu ◽  
Shota Inoue ◽  
...  
Keyword(s):  
Surface Roughness ◽  
Friction Coefficient ◽  
Surface Hardness ◽  
Bolted Joints ◽  
Friction Coefficients ◽  
Clamp Force

In bolted joints, clamp force must be accurately controlled to secure their reliability. However, the clamp force varies widely in each tightening because friction coefficients at thread surfaces and bearing surfaces vary in each tightening due to lubricants, configuration error of bolts, surface roughness, and surface hardness, among other things. In this study, we investigated the robustness of polyisobutylene and ISO VG46 machine oil during the tightening process for several parameters of tightening conditions. We especially focused on variations of the friction coefficient between bearing surfaces at an appropriate target clamp force of M8 bolt/nut assemblies and change rates of the friction coefficients from the middle to the end of the appropriate target clamp force. Results showed that the friction coefficients at the target clamp force varied widely if ISO VG46 machine oil was used as a lubricant. In contrast, the variations of the friction coefficients in which polyisobutylene was used for tightening were small. Results also showed that the friction coefficients invariably decreased about 20% from the middle to the end of the target clamp force if ISO VG46 machine oil was used for the lubricant. However, if polyisobutylene was used, the friction coefficients were almost constant for all tightening instances.

Effect of Coating Thickness on the Friction Coefficients and Torque-Tension Relationship in Threaded Fasteners

2008 ◽  
Author(s):  
Amro M. Zaki ◽  
Sayed A. Nassar
Keyword(s):  
Test Data ◽  
Coating Thickness ◽  
Time Data ◽  
Friction Coefficients ◽  
Threaded Fasteners ◽  
Highly Sensitive ◽  
Structural Applications ◽  
Key Factor ◽  
Set Up ◽  
Bearing Friction

This paper experimentally investigates the effect of coating thickness on the thread, bearing friction coefficients and torque-tension relationship in threaded fasteners. The torque-tension relationship is highly sensitive frictional changes. Two different coating thicknesses are investigated using two bolt sizes; realtime test data is collected for two ranges of bolt tension. The experimental set up collects real-time data on the tightening torque, bolt tension, and the corresponding reaction torque. Test data is used for calculating the thread and bearing friction coefficients, as well as the overall torque-tension relationship for two different coating thicknesses. The study would provide an insight into the variation of the torque-tension relationship which is a key factor that significantly affect the reliability and safety of bolted assemblies in many mechanical and structural applications.

Novel Formulation of the Tightening and Breakaway Torque Components in Threaded Fasteners

2006 ◽  
Author(s):  
Sayed A. Nassar ◽  
Xianjie Yang
Keyword(s):  
Contact Pressure ◽  
Static Friction ◽  
Bolted Connections ◽  
Friction Coefficients ◽  
Difference Analysis ◽  
Threaded Fasteners ◽  
Thread Profile ◽  
Percent Difference ◽  
Breakaway Torque ◽  
Torque Values

New formulas are developed for the torque-tension relationship, various torque components, and for the break-away torque values in threaded fastener applications. The 3-D aspects of the lead helix and thread profile angles, the kinetic and static friction coefficients are all taken into account. Two scenarios of the contact pressure between threads and under the turning fastener head are considered; namely, uniform distributed and linearly distributed contact pressure scenarios. The effect of thread pitch, lead helix and thread profile angles, friction coefficients, and the fastener geometry is discussed. Results from the new formulas are compared with the approximate torque-tension relationship provided in the literature. A percent difference analysis indicates that the new formulas provide significant improvement that would enhance the reliability and safety of bolted connections, especially in critical applications.

Effect of Thread and Bearing Friction Coefficients on the Vibration-Induced Loosening of Threaded Fasteners

2007 ◽  
Vol 129 (4) ◽  
pp. 484-494 ◽  
Author(s):  
Basil A. Housari ◽  
Sayed A. Nassar
Keyword(s):  
Mathematical Model ◽  
The Self ◽  
Time Data ◽  
Friction Coefficients ◽  
Rotational Angle ◽  
Transverse Loads ◽  
Threaded Fasteners ◽  
Solid Film ◽  
Loosening Rate ◽  
Bearing Friction

This study provides a theoretical and experimental investigation of the effect of the thread and bearing friction coefficients on the self-loosening of threaded fasteners that are subjected to cyclic transverse loads. The friction coefficients are varied by using different types of coating and lubrication. A phosphate and oil coating and an olefin and molydisulfide solid film lubricant are used on the bolts tested. A mathematical model is developed to evaluate the self-loosening behavior in threaded fasteners when subjected to cyclic transverse loads. An experimental procedure and test setup are proposed in order to collect real-time data on the loosening rate (rate of clamp load loss per cycle) as well as the rotational angle of the bolt head during its gradual loosening. The experimental values of the friction coefficients are used in the mathematical model to monitor their effect on the theoretical results for the loosening rate. Experimentally, the friction coefficients are modified by changing the coating or the lubrication applied to the fasteners. The theoretical and experimental results are presented and discussed.

scholarly journals Sliding abrasive wear when combining WEDM conditions and polishing treatment on H13 disks over 1045 carbon steel pins

2021 ◽  
Author(s):  
Antonio J. Sánchez Egea ◽  
Vitaliy Martynenko ◽  
Alejando Simoncelli ◽  
Gil Serrancoli ◽  
Daniel Martínez Krahmer
Keyword(s):  
Surface Roughness ◽  
Surface Properties ◽  
Electrical Discharge ◽  
High Speed ◽  
Electrical Discharge Machining ◽  
Wire Electrical Discharge Machining ◽  
Initial Surface ◽  
Friction Coefficients ◽  
Surface Conditions ◽  
Aisi 1045

AbstractForging dies are crucial in forging to manufacture accurate workpieces. These dies are generally made of AISI H steel series and hardened and tempered medium carbon alloy steel. Dies are processed by using high-speed milling + polishing or electrical discharge machining + polishing. The surface quality of the workpiece depends on the surface properties of these dies, where surface roughness, material hardness, and wear evolution of their surfaces are critical aspects to consider. This research analyzes different wire electrical discharge machining surface conditions combined with polishing treatment to describe their influence on friction and wear. Wire electrical discharge machining defines the disks’ surface properties in finishing and roughing conditions, and polishing treatment varies in time and paper sand depending on the roughness. Abbott-Firestone curves and Rsk-Rku roughness parameters characterize the surface roughness of each studied configuration. Room temperature pin-on-disk tests were performed to analyze friction coefficients and wear rate for AISI 1045 pins and AISI H13 disks. On average, the highest (0.284) and the lowest (0.201) friction coefficients were found for the combination of finishing wire electrical discharge machining + polishing and roughing wire electrical discharge machining conditions, respectively. Scanning electron microscope images were taken to describe the wear tracks and pin degradation for different sliding abrasive configurations. The diagram correlating the surface morphology and the friction coefficient predicts the wear damage on initial surface conditions, which is crucial in the forging industry to determine tool maintenance or replacement.

Sign in / Sign up

Export Citation Format

Share Document