Fatigue Calculators

Fatigue Calculation Based on Test or Operation Results

This calculation determines the resource of the product based on the test results or experimental operation of its prototype.

The algorithm determines the fatigue strength reduction factor K of the prototype and applies it to a product being designed.

In the absence of information on the fatigue strength of material σ_-1, it can be determined based on the ultimate strength σ_m. The calculated value of the fatigue limit σ_-1calc can be used in further calculations.

INITIAL DATA

σ_{max_sample} - Maximum equivalent stress during tests or operation at the point of sample failure;

σ_{min_sample} - Minimum equivalent stress during tests or operation at the point of sample failure;

σ_{m_sample} - Ultimate tensile strength of sample material;

σ_{-1_sample} - Fatigue strength of sample material;

N_sample - Number of load cycles before sample failure;

σ_{max_item} - Maximum equivalent stress of the cycle for calculated product;

σ_{min_item} - Minimum equivalent stress of the cycle for calculated product;

σ_{m_item} - Ultimate tensile strength of material of the calculated product;

σ_{-1_item} - Fatigue strength of material of the calculated product.

RESULTS DATA

σ_{-1_calc_sample} - Calculated fatigue strength of sample material. It can be applied if the values of fatigue strength for thr material are absent in standards;

σ_{-1p_sample} - Fatigue strength of sample;

K - Fatigue strength reduction factor. It is equal for sample and for calculated product;

σ_{-1_calc_item} - Calculated fatigue strength of material of the calculated product.

N_calc - Number of load cycles before calculated product failure;

n - Safety factor for calculated product.

Metric Imperial

Maximum stress (σ_{max_sample})

Minimum stress (σ_{min_sample})

Tensile strength (σ_{m_sample})

Fatigue strength (σ_{-1_sample})

Number of load cycles (N_sample)

Fatigue strength (σ_{-1_calc_sample})

Fatigue strength (σ_{-1p_sample}), МПа

Fatigue reduction factor (K)

Maximum stress (σ_{max_item})

Minimum stress (σ_{min_item})

Tensile strength (σ_{m_item})

Fatigue strength (σ_{-1_item})

Fatigue strength (σ_{-1_calc_item})

Number of load cycles (N_calc)

Safety factor (n)

BASIC FORMULAS

Fatigue strength:

σ_{-1_calc_sample} = [(55/100) - (1/10000)*σ_{m_sample}]*σ_{m_sample};

Fatigue reduction factor (for σ_min = -1*σ_max and τ_min = τ_max):

σ_{max_sample}^m * N_sample = σ_{-1p_sample}^m * N_G;

m = [5 + σ_{m_sample}(MPa) / 80] / K;

K = σ_{-1_sample} / σ_{-1p_sample};

N_G = 2*10⁶ - base number of cycles to failure;

The found fatigue strength reduction factor K is applied in the further calculation.

INITIAL DATA

σ_{max_sample} - Maximum equivalent stress during tests or operation at the point of sample failure;

σ_{min_sample} - Minimum equivalent stress during tests or operation at the point of sample failure;

σ_{m_sample} - Ultimate tensile strength of sample material;

σ_{-1_sample} - Fatigue strength of sample material;

N_sample - Number of load cycles before sample failure;

σ_{max_item} - Maximum equivalent stress of the cycle for calculated product;

σ_{min_item} - Minimum equivalent stress of the cycle for calculated product;

σ_{m_item} - Ultimate tensile strength of material of the calculated product;

σ_{-1_item} - Fatigue strength of material of the calculated product.

RESULTS DATA

σ_{-1_calc_sample} - It can be applied if the values of fatigue strength for thr material are absent in standards;

σ_{-1p_sample} - Fatigue strength of sample;

K - Fatigue strength reduction factor. It is equal for sample and for calculated product;

σ_{-1_calc_item} - Calculated fatigue strength of material of the calculated product.

N_calc - Number of load cycles before calculated product failure;

n - Safety factor for calculated product.

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IMPACT LOADS

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DRIVES

FATIGUE

HEAT TRANSFER