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In this study, the experimental apparatus with a friction stir welding dynamometer was employed to investigate the joint characteristics of Cu-Ni alloy plate in thickness of 3.6mm lap-welding to low carbon steel plate in thickness of 4 mm using cylinder type tool (without probe) under the welding parameters of rotating speeds (800~1400 rpm) and traveling speed of tool (10~80 mm/min). To prevent the joint interface from oxidizing during the welding process, the joint interfaces of Cu-Ni alloy and low carbon steel respectively were electroplated with Ni coating layer in different thicknesses before the welding. The effect of the thickness of Ni coating layer on shear strength of joint interface and the mechanism of welding are also investigated. Experimental results show that under the rotating speed of 1000 rpm and travelling speed of 10 mm/min, the shear strength for without Ni coating layer is measured about 100 MPa. On the other hand, the shear strength is increased to saturated value of 290 MPa with increasing the thickness of Ni coating layer. Especially, the shear strength of joint interface for the Cu-Ni alloy with 5£gm thickness of Ni coating layer lap-welding to low carbon steel with thickness of 20£gm thickness of Ni coating layer is about 2.9 times of that for without Ni coating layer. Moreover, the downward force (Fd) is decreased and the maximum interface temperature (Tmax) and shear strength (£n) are increased with increasing the rotating speed (N). The downward force is increased and the maximum interface temperature and shear strength are decreased with increasing the traveling speed (f). This complex relationship is discussed by the new parameter of Fd¡EN/f, the relationship among Fd¡EN/f, maximum interface temperature and shear strength shows that the maximum interface temperature is increased and shear strength is increased to saturated value of 290 MPa with increasing Fd¡EN/f. The phenomenon is explained that the diffusion bonding between the joint interface of two plates become more homogeneous.

The San Andreas Fault (SAF) near Parkfield, CA moves by a combination of aseismic creep and micro-earthquake slip. Measurements of in situ stress orientation, stress magnitude, and heat flow are incompatible with an average shear stress on the SAF greater than approximately 20 MPa. To investigate the micro-mechanical processes responsible for the low strength and creeping behavior, gouge samples from the 3 km-deep scientific borehole near Parkfield (the San Andreas Fault Observatory at Depth, SAFOD) are sheared in a triaxial rock deformation apparatus at conditions simulating those in situ, specifically a temperature of 100°C, effective normal stress of 100 MPa, pore fluid pressure of 25 MPa, and a Na-Ca-K pore fluid chemistry. The 2 mm-thick gouge layers are sheared to 4.25 mm at shear rates of 6.0, 0.6, 0.06, and 0.006 mu m/s. The mechanical data are corrected for apparatus effects and the strength of the jacketing material that isolates the sample from the confining fluid. Experiments indicate that gouge is extremely weak with a coefficient of friction of 0.14, and displays velocity and temperature strengthening behavior. The frictional behavior is consistent with the inferred in situ stress and aseismic creep observed at SAFOD. The low frictional strength likely reflects the presence of a natural fabric characterized by microscale folia containing smectite and serpentinite.

Abstract The rolling is an efficient and economical approach for the manufacturing of strip or plate metals, it plays an important role because of its versatility and its high production rate in the manufacture of various products with uniform cross-sectional area. Without the knowledge of the influences of the variables such as friction conditions, material properties, and workpiece geometry on the process mechanics, it will not be possible to design and control the equipment adequately, or to predict and prevent the occurrence of failures. According to modeling by numerical has become a major tool in rolling research. By using the proper criterion, de-pending upon the production requirements along with the modeling results, the process efficiency, productivity and quality can be increased and the down time of the mill and cost operation can be reduced. In this study, investigated that it do not consider to work hardening and consider to work hardening during the rolling process from Von Karman theory. We can realize friction coefficient, reduction ratio, rolling force, rolling torque, neutral point, and pressure distribution relation, then from measuring rolling force, torque, neutral point can inverse to solve friction coefficient and pressure distribution. Result that we found the error of direct and inverse solution about rolling friction coefficient was less than 5 %, and the coef-ficient of friction was found to increase with reduction and rolling force and neutral point.

ABSTRACT The objective of this study is to obtain the friction coefficient of lubricants in tube hydroforming of guiding zone. Lubricants, universal testing machine, and friction test machine in tube hydroforming of guiding zone are used to carry out the experiments of aluminum alloy tubes. Lubricants are categorized according to their performance as follows: (1) oils, (2) emulsions, and (3) slide lacquer. Different lubricants tests, it is known that the best lubrication is derived from slide lacquer, while oils showed the poorest behavior. Different internal pressure tests, it is known that greater internal pressure causes the coefficient of friction decreasing. Different sliding velocity, it is known that sliding velocity does not affect the coefficient of friction at 100mm/min. And using CCD which is an optical instrument obtains the surface of tubes after experiments.

In this paper, the slipping friction is considered in the problem of a progressive wave of real fluids propagating over a permeable bottom. In the interface of soil and fluid, the ¡§no-slip¡¨ condition is relaxed and a sliding friction coefficient is introduced. Thus, the slipping effect and the permeability of bottom on the velocity near the seabed can be studied. The results indicate that the joint effect of slipping friction and permeability is crucial. The overshooting phenomena also can be explained by this joint effect.

Friction Stir Welding(FSW) experiments are conducted using 6061-T6 aluminum as specimens. The temperatures at different distances from the center of the joint are measured. Curve fitting analyses are used to predict the temperature distribution and calculate the central temperature of the joint, proceeding by measuring temperature. A second order curve is found to better fit the experiment values by the least square method.

In this research, one solid state processing technique, friction stir processing, is applied to modify the AZ61 magnesium alloy billet and to incorporate 5-10 vol% nano-sized ceramic particles SiO2 into the AZ61 magnesium alloy matrix to form bulk composites, using the characteristic rotating downward and circular material flow around the stir pin. The microstructure and mechanical properties of the modified alloy and composite samples are examined and compared. The FSP modified AZ61 alloy could be refined to 3-8um via the dynamic recrystallization during processing. However, the one-pass FSP modified alloy appeared the inhomogeneous grain structures to influence the tensile ductility along the welding direction at elevated temperatures due to the onion splitting. In contrast, the multi-pass FSP could improve the inhomogeneous grain structures to reduce the influence of the onion-splitting to the deformation at elevated temperatures. The FSP modified alloys show the lower yielding stress due to the unique texture of (0002) basal planes, with roughly surround the pin column surface of the pin tool in the stirred zone. In addition, it is suggested that the second processing of the subsequent compression along the normal direction might be necessary to alter the texture and to improve the lower yielding stress after modifying the grain size by FSP. Friction stir processing could successfully fabricate bulk AZ61 Mg based composites with 5 to 10 vol% of nano-sized SiO2 particles. The nano-sized SiO2 particles added into magnesium matrix could be uniformly dispersed after four FSP passes. The average grain sizes of the composites varied within 0.5-2um, and the composites nearly double the hardness as compared with the as-received AZ61 cast billet. This composite exhibited high strain rate superplasticity, with a maximum ductility of 470% at 1x10-2 s-1 and 300oC or 454% at 3x10-1 s-1 and 400oC while maintaining fine grains less than 2um in size.

Friction stir process (FSP) was employed to investigate the grain evolution of AA1050 aluminum alloy in this study. The rotation speeds for the tool were set from 500 to 2000 rpm with a constant traverse speed of 0.5mm/s. The temperature under pin was measured by K-type thermocouple imbedded under the pin. Grain sizes were determined by scanning electron microscopy. The maximum temperature at the bottom of pin increased with the increasing of rotation speed but not exceeding 0.8Tm. Grain size at center and bottom of stirred zone was in linear increase at low rotation speed, but increased a little at high rotation speed (>1000rpm). The grain size grew rapidly into a stable size in a 2mm distance measured from the passing of pin. When rotation speed is above 1000rpm, average grain growth rate is 1£gm/s. When rotation speed is lower than 700rpm, average grain growth rate is slower than 0.2£gm/s. BEI/ECCI observations revealed that grains in SZ became equaxied.

The mechanical properties of the amorphous bulk metallic glassy (BMG) alloy, Mg58Cu31Y11, are examined by a non-traditional analytic method - nanoindentation scratch test. This thesis will discuss the influences of friction force, and fracture surface geometry on the BMG surface for load, depth of scratch, scratch velocity, and test temperature of the nano-scratch process. In this study, experimental factors, including load, depth of scratch, scratch velocity, and test temperature, are taken into consideration to investigate the effects of the friction force. And then, this research utilizes regression analysis to establish BMG machining experience formula. The significant parameters of the friction force on nano-scratch and the reliability of the prediction model are investigated by statistical software. According to the results, the friction force is nearly proportional to power of the load. The friction force exhibits a slightly dependence on the test temperature. Besides, the nano-scratch results show that the friction coefficient also increases as the load and test temperature increases. The results associated with the analysis of the variance can be practiced to assess the prominence among experimental factors. The analysis indicates that the load, test temperature play significant factors on the friction force. The results of the regression analysis using a statistical software can be applied to model the mathematical relationship between machining factors and friction force. It anticipates that the model is able to predict friction force over a wide variety of scratching conditions. The model is also proved in good agreement with experimental results.