Fretting-Fatigue Damage-Factor Determination

1965 ◽  
Vol 87 (3) ◽  
pp. 298-302 ◽  
Author(s):  
J. A. Collins
Keyword(s):  
Fatigue Damage ◽  
Normal Force ◽  
Experimental Tests ◽  
Fretting Fatigue ◽  
Damage Factor ◽  
Sliding Motion ◽  
Static Tensile ◽  
Tentative Explanation ◽  
Solid Bodies ◽  
Static Tensile Stress

Small-amplitude cyclic sliding motion at the interface between two solid bodies pressed together by a normal force initiates microcracks which propagate and cause premature fatigue failure. This action is defined to be fretting-fatigue. A quantitative evaluation of fretting-fatigue damage would be of great value to the mechanical engineering designer. It is proposed that a fretting-fatigue damage-factor could be developed to provide a quantitative index to fretting-fatigue damage. The damage-factor proposed is a function of eight basic fretting-fatigue parameters. Experimental tests were conducted to establish quantitative values for the fretting-fatigue damage-factor for a few specific sets of fretting-fatigue conditions. An unexpected trend in the value of the fretting-fatigue damage-factor was observed for the case of static stress in the specimen during fretting. With a static tensile stress in the specimen during fretting, the fretting-fatigue damage, as measured by reduction in fatigue limit, was very slight, while with a static compressive stress in the specimen during fretting, the fretting-fatigue damage was very great. A tentative explanation is presented.

Fatigue Damage Prediction for Combined Random and Static Mean Stresses

1993 ◽  
Vol 36 (3) ◽  
pp. 25-32
Author(s):  
Ronald Lambert
Keyword(s):  
Fatigue Life ◽  
Fatigue Damage ◽  
Narrow Band ◽  
Stress Rupture ◽  
Structural Elements ◽  
Damage Prediction ◽  
Static Tensile ◽  
Analytical Expressions ◽  
Static Tensile Stress ◽  
Mean Stresses

Closed form analytical expressions have been derived and are proposed for use to predict accumulated fatigue damage and fatigue life of structural elements subjected to a combination of fully reversed narrow-band Gaussian random and static mean stresses. Such mean stresses can significantly alter fatigue life. The proposed method of combining random alternating and mean stresses shows excellent agreement with published experimental data for a steel alloy. Reasonable agreement is maintained, surprisingly, even for static tensile stress values up to near the material's yield stress where the failure mode shifts from that of typical brittle fatigue to that of stress rupture (i.c.,creep). Numerical examples are provided to illustratc the application.

The analysis on the influence of mixed sliding-rolling motion mode to precision degradation of ball screw

2021 ◽  
pp. 095440622098201
Author(s):  
Qiang Cheng ◽  
Baobao Qi ◽  
Hongyan Chu ◽  
Ziling Zhang ◽  
Zhifeng Liu ◽  
...  
Keyword(s):  
Structural Parameters ◽  
Experimental Tests ◽  
Theoretical Models ◽  
Operating Conditions ◽  
Ball Screw ◽  
Rolling Motion ◽  
Degradation Model ◽  
Sliding Motion ◽  
Factors Analysis ◽  
Motion Mode

The combination of sliding/rolling motion can influence the degree of precision degradation of ball screw. Precision degradation modeling and factors analysis can reveal the evolution law of ball screw precision. This paper presents a precision degradation model for factors analysis influencing precision due to mixed sliding-rolling motion. The precision loss model was verified through the comparison of theoretical models and experimental tests. The precision degradation due to rolling motion between the ball and raceway accounted for 29.09% of the screw precision loss due to sliding motion. Additionally, the total precision degradation due to rolling motion accounted for 21.03% of the total sliding precision loss of the screw and nut, and 17.38% of the overall ball screw precision loss under mixed sliding-rolling motion. In addition, the effects of operating conditions and structural parameters on precision loss were analyzed. The sensitivity coefficients of factors influencing were used to quantitatively describe impact degree on precision degradation.

scholarly journals Fatigue Strength Analysis and Fatigue Damage Evaluation of Roller Chain

Metals ◽  
2018 ◽  
Vol 8 (10) ◽  
pp. 847 ◽  
Author(s):  
Ryoichi Saito ◽  
Nao-Aki Noda ◽  
Yoshikazu Sano ◽  
Jian Song ◽  
Takeru Minami ◽  
...  
Keyword(s):  
Fatigue Crack ◽  
Fatigue Strength ◽  
Fatigue Damage ◽  
Fatigue Crack Initiation ◽  
Strength Analysis ◽  
The Finite Element Method ◽  
Roller Chain ◽  
Press Fitting ◽  
The Press ◽  
Static Tensile

This paper deals with the roller chain commonly used for transmission of mechanical power on many kinds of industrial machinery, including conveyors, cars, motorcycles, bicycles, and so forth. It consists of a series of four components called a pin, a bush, a plate, and a roller, which are driven by a sprocket. To clarify the fatigue damage, in this paper, the finite element method (FEM) is applied to those components under three different types of states, that is, the press-fitting state, the static tensile state, and the sprocket-engaging state. By comparing those states, the stress amplitude and the average stress of each component are calculated and plotted on the fatigue limit diagram. The effect of the plastic zone on the fatigue strength is also discussed. The results show that the fatigue crack initiation may start around the middle inner surface of the bush. As am example, the FEM results show that the fatigue crack of the inner plate may start from a certain point at the hole edge. The results agree with the actual fractured position in roller chains used in industry.

A Self-Actuating Traction-Drive Speed Reducer

2004 ◽  
Vol 127 (4) ◽  
pp. 631-636 ◽  
Author(s):  
Donald R. Flugrad ◽  
Abir Z. Qamhiyah
Keyword(s):  
Friction Coefficient ◽  
Normal Force ◽  
Drive System ◽  
Traction Drive ◽  
Sliding Motion ◽  
Output Torque ◽  
Speed Reducer ◽  
Rolling Elements ◽  
Drive Speed ◽  
High Output

Traction-drive speed reducers offer certain advantages over geared speed reducers. In particular, they generally run quieter than geared units and provide an opportunity for higher efficiency by eliminating sliding motion between contacting elements. In order to generate a sufficiently high output torque, some means must be provided to create a normal force between the rolling elements. This normal force, along with the friction coefficient, enables the device to transmit torque from one rolling member to the next. The speed reducer proposed here is designed so that the configuration of the rolling elements creates the needed normal force in response to the torque exerted back on the system by the downstream loading. Thus the device is self-actuating. Since the normal force is only present when needed, the rolling elements of the device can readily be disengaged, thus eliminating the need for a separate clutch in the drive system. This feature can be exploited to design a transmission with several distinct speed ratios that can be engaged and disengaged in response to changing speed requirements.

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