When energetic heavy ions irradiate a deuteride titanium target, a number of recoil deuterium atoms are produced in the solid. The recoil deuterium atoms cause deuteron-deuteron (d-d) fusion reactions in solids. The probability of the d-d fusion reaction has been calculated for the primary colliding deuterium atoms, as well as the collision cascade deuterium atoms. Based on calculated results, an experiment using a heavy-ion accelerator was proposed to study d-d fusion in solids. The enhancement effect on d-d fusion in solids is particularly interesting. The experimental parameters were as follows: The energy of the ion beam for the d-d fusion experiment was in the range from several to several tens of mega-electron-volts for an experiment with an iodine ion beam and a titanium target. The enhancement effect in the solid is evaluated by comparing the experimental results with the present calculated results. The existence of the enhancement at low energies can be confirmed by measuring the depth profile of the fusion probabilities. Reported experimental data have been analyzed by the calculated results. The enhancement has not been found in the data.